CONCORD, N.C.—NASCAR Sprint Cup drivers and teams continued the learning process of the 2013 Cup car Tuesday during an open test session at Charlotte Motor Speedway.

As they spent nearly six hours on the 1.5-mile track, with another six hours scheduled for Wednesday, teams ran through a variety of setups to learn how the new car reacts to different shocks, springs and other aerodynamic configurations.

About 10 of the 16 drivers did 15-lap runs together, where they tried to pass and see how the car handled in traffic.

What did they learn? That there’s still a lot to learn.

“I thought it was similar to the other car (in traffic),” said Joe Gibbs Racing driver Matt Kenseth. “When I pulled out there and I got around them other guys, if you had told me it was last year’s car, I don’t know if I would have known a difference.

“That is probably a good thing because in the early stages of developing anything, usually everybody thinks it’s worse. I didn’t see anything that was any worse than what we had.”

The new cars have distinct bodies for each manufacturer that give them more distinctive characteristics that resemble the passenger cars. While the previous car had virtually the same body for every car, now just the decklids are the same for the three manufacturers. That means each will handle differently under certain circumstances.

“They’re (each) different,” NASCAR vice president of competition Robin Pemberton said about the manufacturer bodies. “The balance on the cars is different. We’ve given enough different things on the car underneath that they can tune on and work on that they can change some of that stuff.”

Gone are rear swaybars (except for road courses) as well as other rear suspension pieces that teams used to skew the rear car as it went from the turns to the straightaway. NASCAR has allowed teams more rear camber, which has increased grip. It also is using a bigger spoiler, which has increased rear downforce. The cars also are 160 pounds lighter than a year ago.

Some of the teams used cars Tuesday that were 100 percent up to date with the current rules. Other teams used cars that still had carbon fiber bodies that were cheaper to build and test. They know the car is still a work in progress.

“We may still implement rules to help them run in traffic,” Pemberton said. “We are going to continue to work on that and won’t quit.”

NASCAR also is looking long term at decreased horsepower and hoped that some teams would try to run the reduced horsepower package so it could get feedback.

But beyond that, NASCAR asked little of the teams. This test was meant for those teams that haven’t had much time to test because they had concentrated primarily on the end of the 2012 season.

Richard Childress Racing’s Jeff Burton posted the fast speed of the morning session at 190.833 mph. In the afternoon session, Regan Smith, driving a Hendrick Motorsports car, posted the top speed of 190.215.

With temperatures in the mid-50s, the conditions were optimal for peak performance and grip. And with no technical inspection and cars in different stages of rules conformity, it was still difficult to tell how different the cars were than last year.

“I just feel like we’ve got a lot more grip, which I think we do,” said Kenseth, who was testing a JGR car for the first time after spending the past 13 years driving a Cup car for Jack Roush.

“Some of the mechanical stuff they did with the rear end (has changed and) I think we have a little bit more downforce than what we had before and we have a nice, cool day.

“I just feel like we have more grip. Other than that, I don’t really notice a big difference, but it is my first time in a car.”

Teams will get a test session Jan. 10-12 at Daytona International Speedway and then be back Jan. 17-18 at Charlotte. In addition to unlimited testing at tracks that don’t hold NASCAR national series events, each organization can pick four Cup tracks to test at during the year.

Pemberton said in addition to those tests, NASCAR will have an open test day the Thursday before weekends start at Las Vegas and Texas in the spring and will have additional practice time during the Auto Club Speedway race weekend in Fontana, Calif.